Fix MSYS2 build

cmake/build_win32.sh

@@ -25,7 +25,7 @@ if [ -z "$MSYSCON" ]; then
 		TOOLCHAIN="$DIR/toolchains/Ubuntu-MinGW-W64-$ARCH.cmake"
 	fi
 else
-	CMAKE_OPTS="$CMAKE_OPTS -DLMMS_BUILD_MSYS=1"
+	TOOLCHAIN="$DIR/toolchains/MSYS-$ARCH.cmake"
 fi
 
 export PATH=$MINGW/bin:$PATH

cmake/toolchains/MSYS-32.cmake

@@ -1,2 +1,4 @@
-INCLUDE(common/Win32)
-SET(LMMS_BUILD_MSYS 1)
+INCLUDE(${CMAKE_CURRENT_LIST_DIR}/common/MSYS.cmake)
+INCLUDE(${CMAKE_CURRENT_LIST_DIR}/common/Win32.cmake)
+
+SET(MINGW_PREFIX                /mingw32)

cmake/toolchains/MSYS-64.cmake

@@ -1,6 +1,5 @@
-INCLUDE(MSYS-32)
-INCLUDE(Win64)
-SET(LMMS_BUILD_MSYS 1)
+INCLUDE(${CMAKE_CURRENT_LIST_DIR}/common/MSYS.cmake)
+INCLUDE(${CMAKE_CURRENT_LIST_DIR}/common/Win64.cmake)
 
 SET(MINGW_PREFIX                /mingw64)
 SET(MINGW_PREFIX32              /mingw32)

cmake/toolchains/common/MSYS.cmake

@@ -2,6 +2,7 @@
 SET(CMAKE_FIND_ROOT_PATH            ${MINGW_PREFIX})
 SET(CMAKE_INSTALL_PREFIX            ${MINGW_PREFIX})
 
+
 # Windows msys mingw ships with a mostly-suitable preconfigured environment
 SET(STRIP                       ${MINGW_PREFIX}/bin/strip)
 SET(CMAKE_RC_COMPILER           ${MINGW_PREFIX}/bin/windres)
@@ -31,4 +32,6 @@ SET(QT_OVERRIDE_LIBRARIES
 IF(LMMS_BUILD_MSYS AND CMAKE_BUILD_TYPE STREQUAL "Debug")
 	# Override Qt debug libraries with release versions
 	SET(QT_LIBRARIES "${QT_OVERRIDE_LIBRARIES}")
-ENDIF()
+ENDIF()
+
+SET(LMMS_BUILD_MSYS 1)